Media access control protocol for multi-hop network systems and method therefore

ABSTRACT

A method and system for wireless communication in which a plurality of media access control (“MAC”) packet data units (“PDUs”) corresponding to a plurality of wireless communication connections are received. The plurality of MAC PDUs is grouped into a relay packet and the relay packet is transmitted. Such grouping and transmission of the relay packet is performed by one or more relay nodes. The traffic control for the transmission can also be based on centralized or decentralized routing control and/or centralized or decentralized QoS control.

FIELD OF THE INVENTION

The present invention relates to the field of wireless communicationsand more particularly to a multi-hop network method and system using anefficient MAC protocol.

BACKGROUND OF THE INVENTION

As the demand for high speed broadband networking over wirelesscommunication links increases, so too does the demand for differenttypes of networks that can accommodate high speed wireless networking.For example, the deployment of IEEE 802.11 wireless networks in homesand business to create Internet access “hot spots” has become prevalentin today's society. However, these IEEE 802.11 based networks arelimited in bandwidth as well as distance. For example, maximum typicalthroughput from a user device to a wireless access point is 54 MB/sec.at a range of only a hundred meters or so. In contrast, while wirelessrange can be extended through other technologies such as cellulartechnology, data throughput using current cellular technologies islimited to a few MB/sec. Put simply, as the distance from the basestation increase, the need for higher transmission power increases andthe maximum data rate typically decreases. As a result, there is a needto support high speed wireless connectivity beyond a short distance suchas within a home or office.

As a result of the demand for longer range wireless networking, the IEEE802.16 standard was developed. The IEEE 802.16 standard is oftenreferred to as WiMAX or less commonly as WirelessMAN or the AirInterface Standard. This standard provides a specification for fixedbroadband wireless metropolitan access networks (“MAN”s) that use apoint-to-multipoint architecture. Such communications can beimplemented, for example, using orthogonal frequency divisionmultiplexing (“OFDM”) communication. OFDM communication uses a spreadspectrum technique distributes the data over a large number of carriersthat are spaced apart at precise frequencies. This spacing provides the“orthogonality” that prevents the demodulators from seeing frequenciesother than their own.

The 802.16 standard supports high bit rates in both uploading to anddownloading from a base station up to a distance of 30 miles to handlesuch services as VoIP, IP connectivity and other voice and data formats.Expected data throughput for a typical WiMAX network is 45 MBits/sec.per channel. The 802.16e standard defines a media access control (“MAC”)layer that supports multiple physical layer specifications customizedfor the frequency band of use and their associated regulations. However,the 802.16e standard does not provide support for multi-hop networks.802.16 networks, such as 802.16j networks, can be deployed as multi-hopnetworks from the subscriber equipment to the carrier base station. Inother words, in multi-hop networks, the subscriber device cancommunicate with the base station directly or through an intermediatedevice.

The complexity involved in supporting multi-hop networks in a robustmanner necessarily involves sophisticated MAC control layer protocols.Such protocols do not exist. For example, as noted above, the IEEE802.16e standard does not support multi-hop networks. The IEEE 802.16jstandard for supporting multi-hop networks has been proposed, but thestandard currently makes no provision for efficient use of MAC layerresources. As such, MAC protocol data units (“PDUs”) in a multi-hopenvironment are not arranged to minimize overhead or provide efficientmeans for relaying control information. For example, current methods donot allow MAC PDUs for multiple connections associated with differentusers to be grouped into a single relay packet. As another example,current methods do not define how route control or quality of service(“QoS”) control within a multi-hop communication network can besupported in centralized or decentralized manners.

It is therefore desirable to have method and system that provides MACPDU arrangements that allow efficient use of MAC layer resources insupporting wireless multi-hop relay networks, including but not limitedto those operating in accordance with the IEEE 802.16 standards.

SUMMARY OF THE INVENTION

The present invention advantageously provides a method and system forwireless communication using relay nodes. Traffic forwarding control,such as routing control and QoS control can be centralized ordecentralized. Arrangements for security and the suppression oftransmission of redundant information are also provided.

In accordance with one aspect, the present invention provides a methodfor wireless communication in which a plurality of media access control(“MAC”) packet data units (“PDUs”) corresponding to a plurality ofwireless communication connections are received. The plurality of MACPDUs is grouped into a relay packet and the relay packet is transmitted.

In accordance with another aspect, the present invention provides asystem for wireless communication in which the system includes at leastone relay node. The relay node is arranged to receive a plurality ofmedia access control (“MAC”) packet data units (“PDUs”) corresponding toa plurality of wireless communication connections, group the pluralityof MAC PDUs into a relay packet and transmit the relay packet.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a diagram of an embodiment of a system constructed inaccordance with the principles of the present invention;

FIG. 2 is a block diagram of an exemplary base station constructed inaccordance with the principles of the present invention;

FIG. 3 is a block diagram of an exemplary mobile station constructed inaccordance with the principles of the present invention;

FIG. 4 is a block diagram of an exemplary OFDM architecture constructedin accordance with the principles of the present invention;

FIG. 5 is a block diagram of the flow of received signal processing inaccordance with the principles of the present invention;

FIG. 6 is a diagram of an exemplary scattering of pilot symbols amongavailable sub-carriers;

FIG. 7 is a block diagram of an embodiment of a MAC layer protocol stackconstructed in accordance with the principles of the present invention;

FIG. 8 is a block diagram of another embodiment of a MAC layer protocolstack constructed in accordance with the principles of the presentinvention;

FIG. 9 is a block diagram of an exemplary relay MAC (“R-MAC”) headerformat constructed in accordance with the principles of the presentinvention;

FIG. 10 is a block diagram of another exemplary R-MAC header formatconstructed in accordance with the principles of the present invention;

FIG. 11 is a block diagram of an exemplary combined forwarding QoS androute sub-header constructed in accordance with the principles of thepresent invention; and

FIG. 12 is a block diagram of a data packing arrangement constructed inaccordance with the principles of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It is noted that various multi-hop communication schemes are describedherein in accordance with the present invention. While described in thecontext of the Institute of Electrical and Electronics Engineers(“IEEE”) 802.16 standards, one of ordinary skill in the art willappreciate that the broader inventions described herein are not limitedin this regard and merely for exemplary and explanatory purposes.

According to the present invention, various media access control (“MAC”)layer designs for downlink communications between a base station (“BS”)and a relay station (“RS”) and between a RS and RS are described. One ofordinary skill in the art will appreciate that the invention describedherein is not limited solely to use with downlink communications but isequally applicable to uplink communications as well, for example betweena mobile station (“MS”) and RS, a RS and RS, and a RS and BS.

According to one embodiment of the invention a Relay Station MAC (R-MAC)layer is introduced. According to another embodiment the existing IEEE802.16e MAC is modified to implement and support the features andfunctions described herein.

Referring now to the drawing figures in which like reference designatorsrefer to like elements, there is shown in FIG. 1, a system constructedin accordance with the principles of the present invention anddesignated generally as “10.” System 10 includes base stations 12, relaynodes 14 and mobile stations 16. Base stations 12 communicate with oneanother and with external networks, such as the Internet (not shown),via carrier network 18. Base stations 12 engage in wirelesscommunication with relay nodes 14 and/or mobile stations 16. Similarly,mobile stations 16 engage in wireless communication with relay nodes 14and/or base stations 12.

Base station 12 can be any base station arranged to wirelesslycommunicate with relay nodes 14 and/or mobile stations 16. Base stations12 include the hardware and software used to implement the functionsdescribed herein to support the MAC control plane functions. Basestations 12 include a central processing unit, transmitter, receiver,I/O devices and storage such as volatile and nonvolatile memory as maybe needed to implement the functions described herein. Base stations 12are described in additional detail below.

Mobile stations 16, also described in detail below, can be any mobilestation including but not limited to a computing device equipped forwireless communication, cell phone, wireless personal digital assistant(“PDA”) and the like. Mobile stations 16 also include the hardware andsoftware suitable to support the MAC control plane functions needed toengage in wireless communication with base station 12 either directly orvia a relay node 14. Such hardware can include a receiver, transmitter,central processing unit, storage in the form of volatile and nonvolatilememory, input/output devices, etc.

Relay node 14 is used to facilitate wireless communication betweenmobile station and base station 12 in the uplink (mobile station 16 tobase station 12) and/or the downlink (base station 12 to mobile station16). A relay node 14 configured in accordance with the principles of thepresent invention includes a central processing unit, storage in theform of volatile and/or nonvolatile memory, transmitter, receiver,input/output devices and the like. Relay node 14 also includes softwareto implement the MAC control functions described herein. Of note, thearrangement shown in FIG. 1 is general in nature and other specificcommunication embodiments constructed in accordance with the principlesof the present invention are contemplated.

Although not shown, system 10 includes a base station controller (“BSC”)that controls wireless communications within multiple cells, which areserved by corresponding base stations (“BS”) 12. In general, each basestation 12 facilitates communications using OFDM with mobile stations16, which are within the cell 12 associated with the corresponding basestation 12. The movement of the mobile stations 16 in relation to thebase stations 12 results in significant fluctuation in channelconditions. It is contemplated that the base stations 12 and mobilestations 16 may include multiple antennas in a multiple input multipleoutput (“MIMO”) arrangement to provide spatial diversity forcommunications.

A high level overview of the mobile stations 16 and base stations 12 ofthe present invention is provided prior to delving into the structuraland functional details of the preferred embodiments. It is understoodthat relay nodes 14 can incorporate those structural and functionalaspects described herein with respect to base stations 12 and mobilestations 16 as may be needed to perform the functions described herein.

With reference to FIG. 2, a base station 12 configured according to oneembodiment of the present invention is illustrated. The base station 12generally includes a control system 20 such as a central processingunit, a baseband processor 22, transmit circuitry 24, receive circuitry26, multiple antennas 28, and a network interface 30. The receivecircuitry 26 receives radio frequency signals bearing information fromone or more remote transmitters provided by mobile stations 16(illustrated in FIG. 3). Preferably, a low noise amplifier and a filter(not shown) cooperate to amplify and remove out-of-band interferencefrom the signal for processing. Down conversion and digitizationcircuitry (not shown) then down converts the filtered, received signalto an intermediate or baseband frequency signal, which is then digitizedinto one or more digital streams.

The baseband processor 22 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 22 is generallyimplemented in one or more digital signal processors (“DSPs”) orapplication-specific integrated circuits (“ASICs”). The receivedinformation is then sent across a wireless network via the networkinterface 30 or transmitted to another mobile station 16 serviced by thebase station 12.

On the transmit side, the baseband processor 22 receives digitized data,which may represent voice, data, or control information, from thenetwork interface 30 under the control of control system 20, and encodesthe data for transmission. The encoded data is output to the transmitcircuitry 24, where it is modulated by a carrier signal having a desiredtransmit frequency or frequencies. A power amplifier (not shown)amplifies the modulated carrier signal to a level appropriate fortransmission, and delivers the modulated carrier signal to the antennas28 through a matching network (not shown). Modulation and processingdetails are described in greater detail below.

With reference to FIG. 3, a mobile station 16 configured according toone embodiment of the present invention is described. Similar to basestation 12, a mobile station 16 constructed in accordance with theprinciples of the present invention includes a control system 32, abaseband processor 34, transmit circuitry 36, receive circuitry 38,multiple antennas 40, and user interface circuitry 42. The receivecircuitry 38 receives radio frequency signals bearing information fromone or more base stations 12. Preferably, a low noise amplifier and afilter (not shown) cooperate to amplify and remove out-of-bandinterference from the signal for processing. Down conversion anddigitization circuitry (not shown) then down convert the filtered,received signal to an intermediate or baseband frequency signal, whichis then digitized into one or more digital streams.

The baseband processor 34 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations, as will be discussed on greater detail below. Thebaseband processor 34 is generally implemented in one or more digitalsignal processors (“DSPs”) and application specific integrated circuits(“ASICs”).

With respect to transmission, the baseband processor 34 receivesdigitized data, which may represent voice, data, or control information,from the control system 32, which it encodes for transmission. Theencoded data is output to the transmit circuitry 36, where it is used bya modulator to modulate a carrier signal that is at a desired transmitfrequency or frequencies. A power amplifier (not shown) amplifies themodulated carrier signal to a level appropriate for transmission, anddelivers the modulated carrier signal to the antennas 40 through amatching network (not shown). Various modulation and processingtechniques available to those skilled in the art are applicable to thepresent invention.

In OFDM modulation, the transmission band is divided into multiple,orthogonal carrier waves. Each carrier wave is modulated according tothe digital data to be transmitted. Because OFDM divides thetransmission band into multiple carriers, the bandwidth per carrierdecreases and the modulation time per carrier increases. Since themultiple carriers are transmitted in parallel, the transmission rate forthe digital data, or symbols, on any given carrier is lower than when asingle carrier is used.

OFDM modulation is implemented, for example, through the performance ofan Inverse Fast Fourier Transform (“IFFT”) on the information to betransmitted. For demodulation, a Fast Fourier Transform (“FFT”) on thereceived signal is performed to recover the transmitted information. Inpractice, the IFFT and FFT are provided by digital signal processingcarrying out an Inverse Discrete Fourier Transform (IDFT) and DiscreteFourier Transform (“DFT”), respectively. Accordingly, the characterizingfeature of OFDM modulation is that orthogonal carrier waves aregenerated for multiple bands within a transmission channel. Themodulated signals are digital signals having a relatively lowtransmission rate and capable of staying within their respective bands.The individual carrier waves are not modulated directly by the digitalsignals. Instead, all carrier waves are modulated at once by IFFTprocessing.

In one embodiment, OFDM is used for at least the downlink transmissionfrom the base stations 12 to the mobile stations 16 via relay nodes 14.Each base station 12 is equipped with n transmit antennas 28, and eachmobile station 16 is equipped with m receive antennas 40. Relay nodes 14can include multiple transmit and receive antennas as well. Notably, therespective antennas can be used for reception and transmission usingappropriate duplexers or switches and are so labeled only for clarity.

With reference to FIG. 4, a logical OFDM transmission architecture isdescribed according to one embodiment. Initially, the base stationcontroller 10 sends data to be transmitted to various mobile stations 16to the base station 12. The base station 12 may use the channel qualityindicators (“CQIs”) associated with the mobile stations to schedule thedata for transmission as well as select appropriate coding andmodulation for transmitting the scheduled data. The CQIs may be provideddirectly by the mobile stations 16 or determined at the base station 12based on information provided by the mobile stations 16. In either case,the CQI for each mobile station 16 is a function of the degree to whichthe channel amplitude (or response) varies across the OFDM frequencyband.

The scheduled data 44, which is a stream of bits, is scrambled in amanner reducing the peak-to-average power ratio associated with the datausing data scrambling logic 46. A cyclic redundancy check (“CRC”) forthe scrambled data is determined and appended to the scrambled datausing CRC adding logic 48. Next, channel coding is performed usingchannel encoder logic 50 to effectively add redundancy to the data tofacilitate recovery and error correction at the mobile station 16.Again, the channel coding for a particular mobile station 16 is based onthe CQI. The channel encoder logic 50 uses known Turbo encodingtechniques in one embodiment. The encoded data is then processed by ratematching logic 52 to compensate for the data expansion associated withencoding.

Bit interleaver logic 54 systematically reorders the bits in the encodeddata to minimize the loss of consecutive data bits. The resultant databits are systematically mapped into corresponding symbols depending onthe chosen baseband modulation by mapping logic 56. Preferably,Quadrature Amplitude Modulation (“QAM”) or Quadrature Phase Shift Key(“QPSK”) modulation is used. The degree of modulation is preferablychosen based on the CQI for the particular mobile station. The symbolsmay be systematically reordered to further bolster the immunity of thetransmitted signal to periodic data loss caused by frequency selectivefading using symbol interleaver logic 58.

At this point, groups of bits have been mapped into symbols representinglocations in an amplitude and phase constellation. When spatialdiversity is desired, blocks of symbols are then processed by space-timeblock code (“STC”) encoder logic 60, which modifies the symbols in afashion making the transmitted signals more resistant to interferenceand more readily decoded at a mobile station 16. The STC encoder logic60 will process the incoming symbols and provide n outputs correspondingto the number of transmit antennas 28 for the base station 12. Thecontrol system 20 and/or baseband processor 22 will provide a mappingcontrol signal to control STC encoding. At this point, assume thesymbols for the n outputs are representative of the data to betransmitted and capable of being recovered by the mobile station 16. SeeA. F. Naguib, N. Seshadri, and A. R. Calderbank, “Applications ofspace-time codes and interference suppression for high capacity and highdata rate wireless systems,” Thirty-Second Asilomar Conference onSignals, Systems & Computers, Volume 2, pp. 1803-1810, 1998, which isincorporated herein by reference in its entirety.

For the present example, assume the base station 12 has two antennas 28(n=2) and the STC encoder logic 60 provides two output streams ofsymbols. Accordingly, each of the symbol streams output by the STCencoder logic 60 is sent to a corresponding IFFT processor 62,illustrated separately for ease of understanding. Those skilled in theart will recognize that one or more processors may be used to providesuch digital signal processing, alone or in combination with otherprocessing described herein. The IFFT processors 62 will preferablyoperate on the respective symbols to provide an inverse FourierTransform. The output of the IFFT processors 62 provides symbols in thetime domain. The time domain symbols are grouped into frames, which areassociated with a prefix by like insertion logic 64. Each of theresultant signals is up-converted in the digital domain to anintermediate frequency and converted to an analog signal via thecorresponding digital up-conversion (“DUC”) and digital-to-analog (D/A)conversion circuitry 66. The resultant (analog) signals are thensimultaneously modulated at the desired RF frequency, amplified, andtransmitted via the RF circuitry 68 and antennas 28. Notably, pilotsignals known by the intended mobile station 16 are scattered among thesub-carriers. The mobile station 16, which is discussed in detail below,will use the pilot signals for channel estimation.

Reference is now made to FIG. 5 to illustrate reception of thetransmitted signals by a mobile station 16. Upon arrival of thetransmitted signals at each of the antennas 40 of the mobile station 16,the respective signals are demodulated and amplified by corresponding RFcircuitry 70. For the sake of conciseness and clarity, only one of thetwo receive paths is described and illustrated in detail.Analog-to-digital (“A/D”) converter and down-conversion circuitry 72digitizes and downconverts the analog signal for digital processing. Theresultant digitized signal may be used by automatic gain controlcircuitry (“AGC”) 74 to control the gain of the amplifiers in the RFcircuitry 70 based on the received signal level.

Initially, the digitized signal is provided to synchronization logic 76,which includes coarse synchronization logic 78, which buffers severalOFDM symbols and calculates an auto-correlation between the twosuccessive OFDM symbols. A resultant time index corresponding to themaximum of the correlation result determines a fine synchronizationsearch window, which is used by fine synchronization logic 80 todetermine a precise framing starting position based on the headers. Theoutput of the fine synchronization logic 80 facilitates frameacquisition by frame alignment logic 84. Proper framing alignment isimportant so that subsequent FFT processing provides an accurateconversion from the time to the frequency domain. The finesynchronization algorithm is based on the correlation between thereceived pilot signals carried by the headers and a local copy of theknown pilot data. Once frame alignment acquisition occurs, the prefix ofthe OFDM symbol is removed with prefix removal logic 86 and resultantsamples are sent to frequency offset correction logic 88, whichcompensates for the system frequency offset caused by the unmatchedlocal oscillators in the transmitter and the receiver. Preferably, thesynchronization logic 76 includes frequency offset and clock estimationlogic 82, which is based on the headers to help estimate such effects onthe transmitted signal and provide those estimations to the correctionlogic 88 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready forconversion to the frequency domain using FFT processing logic 90. Theresults are frequency domain symbols, which are sent to processing logic92. The processing logic 92 extracts the scattered pilot signal usingscattered pilot extraction logic 94, determines a channel estimate basedon the extracted pilot signal using channel estimation logic 96, andprovides channel responses for all sub-carriers using channelreconstruction logic 98. In order to determine a channel response foreach of the sub-carriers, the pilot signal is essentially multiple pilotsymbols that are scattered among the data symbols throughout the OFDMsub-carriers in a known pattern in both time and frequency. FIG. 6illustrates an exemplary scattering of pilot symbols among availablesub-carriers over a given time and frequency plot in an OFDMenvironment. Referring again to FIG. 5, the processing logic comparesthe received pilot symbols with the pilot symbols that are expected incertain sub-carriers at certain times to determine a channel responsefor the sub-carriers in which pilot symbols were transmitted. Theresults are interpolated to estimate a channel response for most, if notall, of the remaining sub-carriers for which pilot symbols were notprovided. The actual and interpolated channel responses are used toestimate an overall channel response, which includes the channelresponses for most, if not all, of the sub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information,which are derived from the channel responses for each receive path areprovided to an STC decoder 100, which provides STC decoding on bothreceived paths to recover the transmitted symbols. The channelreconstruction information provides equalization information to the STCdecoder 100 sufficient to remove the effects of the transmission channelwhen processing the respective frequency domain symbols The recoveredsymbols are placed back in order using symbol de-interleaver logic 102,which corresponds to the symbol interleaver logic 58 of the transmitter.The de-interleaved symbols are then demodulated or de-mapped to acorresponding bitstream using de-mapping logic 104. The bits are thende-interleaved using bit de-interleaver logic 106, which corresponds tothe bit interleaver logic 54 of the transmitter architecture. Thede-interleaved bits are then processed by rate de-matching logic 108 andpresented to channel decoder logic 110 to recover the initiallyscrambled data and the CRC checksum. Accordingly, CRC logic 112 removesthe CRC checksum, checks the scrambled data in traditional fashion, andprovides it to the de-scrambling logic 114 for de-scrambling using theknown base station de-scrambling code to recover the originallytransmitted data 116.

FIG. 7 shows a protocol stack 124 for an embodiment of the inventionwhere an R-MAC layer is introduced to facilitate (1) packing multipleMAC PDUs from one CID into one R-MAC PDU for optional 16 e GMHsuppression, (2) packing multiple MAC PDUs from multiple mobile stations16 supported by one RS into one R-MAC PDU to reduce overhead, (3)packing multiple MAC PDUs from multiple mobile stations 16 supported bymultiple RS into one R-MAC PDU to reduce overhead, and (4) packingmultiple MAC PDUs for multiple MSs supported by the same RS into oneR-MAC PDU to reduce overhead.

As is shown, re-fragmentation can be performed at a relay node 14 fortransmission between relay node 14 and mobile stations 16. FIG. 7 showsthe protocol for relaying traffic to a mobile station 16 MS trafficrelaying where mobile station 16 connection and privacy management areperformed on an end-to-end basis. This scenario assumes a transmissionpassed between base station 12 and mobile station 16, and provides tworelay nodes, namely relay nodes 14 a and relay node 14 b in the path. Ofnote, relay nodes 14 a and 14 b are referred to collectively herein asrelay node(s) 14. As such, the diagram in FIG. 7 shows a relay node hopbetween base station 12 and mobile station 16. As is seen in FIG. 7,this arrangement includes a MAC layer for facilitating relay data planefunctions (defined and described herein as the “R-MAC” layer). It isthis R-MAC layer 126 that provides scheduling, flow and routing controlas well as re-fragmentation. R-MAC layer 126 is applicable to the linksbetween base stations 12 and relay stations 14, as well as between relaystations 14. Of note, although shown as R-PHY 128 in FIG. 7, for purephysical layer relaying, the physical layer protocol is the same ascurrent protocols, e.g., the IEEE 802.16d/e protocol stack. R-PHY 128 isused for the convenience of indicating that the physical layercommunication is between base station 12 and relay node 14 or betweenrelay nodes 14.

As is seen in FIG. 7, security at the MAC layer is initiated at basestation 14. Relay nodes 14 include physical layer 128 and R-MAC layer126. Base stations 12 and mobile stations 16 also include a MAC commonprocess sub-layer (“CPS”) 130 for communicating MAC management messages.Relay nodes 14 can implement CPS 130 (not shown) or a sub-set of the CPS130, shown as CPS-lite 132 in FIG. 7. CPS-lite 132 includes support forfunctions such as process (sharing) of MAC management messages betweenbase station 12 and mobile station 16, scheduling on the access link,etc. Base station 12 and mobile station 16 include a MAC securitysub-layer (“MAC-SS”) 134 which provides end-to-end security. Convergencesub-layer (“MAC-CS”) 136 is also provided by base stations 12 and mobilestations 16. Arrangements for providing MAC-SS 134, MAC-CS 136, R-PHY126 as well as general physical layer (“PHY”) 138 for physical layercommunication between relay nodes 14 and mobile stations 14 are known inthe art and are not explained herein.

An alternative protocol stack embodiment constructed in accordance withthe principles of the present invention is shown in FIG. 8. As is shownin FIG. 8, relay nodes 14 can optionally implement R-MAC sub-layer 126,an 802.16e MAC CPS 130 sub-layer such as an IEEE 802.16e CPS sub-layer,and MAC CS 136 sub-layer. In accordance with this embodiment, theprotocol for traffic relay is arranged such that mobile station 16connection and privacy management are managed by relay node 14 and therelay node 14 connection and privacy management are controlled by basestation 12.

It is contemplated that a relay node 14 can implement a variety ofdifferent protocol layers. For example, relay node 14 can implement onlythe R-PHY 128 layer on the relay node 14 to relay node 14 (“R-link”) andthe traditional IEEE 802.16e protocol PHY 138 on the relay node 14 tomobile station 16 access link. As another option, relay node 14 canimplement only R-PHY 128 and R-MAC 126 layers on the R-link. As stillanother option, relay node 14 can implement the R-PHY 128, R-MAC 126 andMAC-CPS 130 layers on the R-link. Finally, relay node 14 can implementthe R-PHY 128, R-MAC 126, MAC-SS 134, MAC-CPS 130 (or MAC-CPS lite 132)and MAC-CS 136 layers on the R-link.

It is contemplated that R-MAC PDU formats can be implemented inaccordance with various embodiments of the present invention. Forexample, an R-MAC PDU can include a 2 bit control field, where the firstbit is a type field in which a “1” indicates the PDU is a control headeronly (without payload) and a “0” indicates that there is a trafficpayload. The second bit can be a receiving relay node ID (“RSID”)indicator in which a “1” indicates that a receiving relay node 14 ID isincluded and a “0” indicates that a receiving relay node 14 ID is notincluded. The RSID may be used to indicate the relay node 14 (alsoreferred to herein as “relay station” 14) that is to receive the R-MACPDU. A length field indicates the total length of the R-MAC PDU. It iscontemplated that the same format for same type of control fields andsub-header can be used.

The R-MAC layer of the present invention provides an extendableframework for various relay related functions, such as QoS control,routing control and etc. An R-MAC PDU may include an R-MAC header,followed by zero or some number of R-MAC sub-headers, with or without anR-MAC payload. The R-MAC payload can include either relay node 14related control messages or MAC PDUs such as IEEE 802.16e MAC PDUs.Although the term “sub-header” is used herein, the invention is notlimited solely to the use of “sub-headers”. Any suitable arrangement forcarrying the information, whether as a sub-header, field, header, etc,can be used.

Two exemplary R-MAC header formats are shown and described withreference to the diagrams of FIGS. 9 and 10. FIG. 9 shows “Type 1” R-MACheader 140. R-MAC header 140 is a control header. As such, thecorresponding R-MAC PDU contains a header but no payload is included.FIG. 10 shows “Type 2” R-MAC header 142. R-MAC header 142 can be usedfor data forwarding. Corresponding R-MAC PDUs with a payload may includetype 2 R-MAC header 142 which may include one or more R-Sub-header(s).

Referring to FIG. 9, the fields of Type 1 R-MAC header 140 areexplained. R-MAC header control (“R-HC”) field 144 is a single bit fielddefining the type of R-MAC header. A “1” indicates that the R-MAC headeris a Type 1 header while a “0” indicates that the R-MAC header is a Type2 header.

RSID inclusion indicator (“RII”) field 146 is a single bit field thatindicates whether or not an RSID is included in the R-MAC header 140 (or142). A “1” indicates that an RSID is included while a “0” indicatesthat an RSID is not included. Control type field 148 is a 4 bit fieldthat indicates the control type. Control content field 150 is a 10 bitfield that contains the control information corresponding to the typeindicated in control content field 148. RSID/control content field 152is an 8 bit field. If RII field 146 is “1”, RSID/control content field152 contains the RSID. If RII field 146 is “0”, RSID/control contentfield 152 contains the control content corresponding to the typeindicated in content field 148. R-MAC header check sequence field 154 isan 8 bit field with a check sequence.

Differences between the format of Type 1 R-MAC header 140 and Type 2R-MAC header 142 are described with reference to FIG. 10. Number ofencapsulated MAC PDUs field 156 is a 6 bit field that indicates thenumber of MAC PDUs, such as the number of IEEE 802.16e MAC PDUsencapsulated in the payload. Number of R-sub-headers field 158 is a 4bit field indicating the quantity of R-sub-headers following the R-MACheader 142. Four bit field 160 is reserved for future use as the use ofR-MAC headers develops. RSID/reserved field 162 is an 8 bit field. IfRII field 146 is “1”, field 162 includes the RSID. If RII field 146 is“0”, field 162 is not used and is reserved for future use. It is notedthat field arrangements and lengths described with reference to FIGS. 9and 10 are merely exemplary and that the fields can be arrangeddifferently and/or have lengths other than those described herein.

The present invention provides for a variety of different arrangementsfor controlling relay packets via traffic control, i.e., routing and QoScontrol. In accordance with one arrangement, decentralized routing andQoS control are provided. Under this arrangement, each forwarding relaynode 14 stores and maintains QoS by connection ID assigned to theconnection between base station 12 and mobile station 16 as well as aroute table (by CID). No control field or sub-header field is used sincethe relay node 14 maintains the information that would have been presentin these fields and sent by base station 12 in a centralizedarrangement.

In accordance with a second arrangement, QoS control is centralized inbase station 14 while route control remains decentralized as describedabove. Here, the forwarding relay node 14 stores and maintains only aroute table at the connection level (CID). Here, a forwarding QoSsub-header can be used. One sub-header may be used for one group of MACPDUs to/from a relay node 14. When more than one group is encapsulated,multiple sub-headers can be used. An exemplary traffic control(forwarding QoS) sub-header supporting grouping can include a fieldindicating the quantity of MAC PDUs to follow along with the number ofMAC PDUs indicated in the quantity field. Each PDU includes a QoS fieldcorresponding to that encapsulated MAC PDU. If only one QoS field isincluded, this indicates that there is either only one encapsulated MACPDU or that the QoS field is applicable to all encapsulated MAC PDUs. Itis noted that the QoS field defines the deadline or other QoS relatedinformation for transmission to the destination mobile station 16.

A number of different exemplary embodiments are contemplated forimplementing decentralized, i.e., distributed, routing control. Oneexample uses mobile station 14 CID-based routing. In accordance withthis example, each relay node 14 maintains a routing table to include asentries all CIDs to be relayed. Each CID is associated with a “next hopRSID”. For each received downlink (“DL”) MAC PDU, relay node 14 checksthe CID through the header of MAC PDU and then delivers the MAC PDU tothe next hop relay node corresponding the CID in the routing table. Inthis example, no modification of the existing IEEE 802.1 6e MAC isrequired.

As another example of decentralized routing control, routing control canbe provided based on the destination RSID or destination CID. In thiscase, the destination RSID is the ID of the relay node 14 that is thedestination of a forward path. Similarly, the destination CID is thebasic CID of the relay node 14 that is the destination of a forwardpath. The destination RSID/CID is carried together along with a MAC PDU.Thus, a destination RSID/CID sub-header is used. Each relay node 14stores and maintains a routing table to include a RSID/CID (destinationRSID/CID) as entries. Each destination RSID/CID is associated with a“next hop RSID”. For each received downlink MAC PDU, the relay node 14checks the destination RSID/CID sub-header and then delivers the MAC PDUto the next hop relay node 14 corresponding to this destination RSID/CIDin the routing table.

As still another example of decentralized routing control, routingcontrol can be provided based on the tunnel CID (“T-CID”) defined for atunnel connection between base station 12 and relay node 14 carryingIEEE 802.16e MAC PDUs. Each T-CID is associated with a particular routeand a set of QoS parameters.

The T-CID information is carried along with a MAC PDU. Thus, a T-CIDsub-header is used. The sub-header is provided such that it can supportthe transport of the T-CID information. Each relay node 14 stores andmaintains a routing table having T-CIDs as entries. Each T-CID isassociated with a “next hop RS” field. After a relay node 14 receives aMAC PDU, the relay node 14 checks the T-CID information and forwardsthis MAC PDU to the next hop relay node 14 corresponding to this T-CIDin the routing table.

For centralized, QoS control, the present invention provides forsource-based QoS control. In the downlink, base station 12 sends the QoSinformation along with a downlink MAC PDU to instruct relay nodes 14 inthe downstream forwarding path how to relay this MAC PDU. In the uplink,the access relay node 14, i.e., the relay node 14 receiving MAC PDUsfrom a mobile station 16, sends the QoS information along with an uplinkMAC PDU to instruct relay nodes 14 in the upstream forwarding path howto relay this MAC PDU. Thus a QoS sub-header such as that describedabove is used. For source-based QoS control, relay nodes 14 do not storeor maintain QoS related information. After a relay node 14 receives aMAC PDU, the relay node 14 checks the QoS information received alongwith this MAC PDU and schedules further transmission of this MAC PDU inaccordance with that QoS information.

In accordance with a third arrangement, routing control is centralizedwithin base station 12 but QoS control is decentralized and provided byforwarding relay node 14 as discussed above. This arrangement alsoallows hybrid route control in which the forwarding relay node 14 storesand maintains the QoS control table (by CID) as well as a route table atthe relay node 14, i.e., by destination relay node 14. In this case, aforwarding route sub-header can be used in which one sub-header may beused for one group of MAC PDUs to/from one relay node 14. When more thanone group of MAC PDUs is encapsulated, multiple such sub-headers may beused.

An exemplary traffic control (forwarding route) sub-header includes afield indicating the quantity of MAC PDUs from or destined to a relaynode 14. Another field indicates the quantity of RSIDs in the forwardingpath included in the sub-header ordered from next hop RSID todestination RSID. If the quantity is 1, the next hop is the destinationRSID. The sub-header also includes a quantity of RSID fields equal tothe value in the quantity of sub-headers field. By way of example, eachRSID field can be an 8 bit field containing the subordinate RSID. Ofnote an RSID is assigned to a relay node 14 when that relay node 14 isregistered within the system 10. Methods for assigning and maintainingRSID lists are known and are not described herein.

An exemplary embodiment for implementing centralized (source) routingcontrol is arranged such that the source routing information includesone or multiple RSIDs of the relay nodes 14 in the forwarding path. Thesource routing information is carried along with a MAC PDU. Thus, asource routing sub-header such as that described above is used. It isnoted that the relay nodes 14 do not maintain any routing table. Foreach received MAC PDU, a relay node 14 simply removes its own RSID inthe source routing sub-header and forwards this MAC PDU to the nextrelay node 14 corresponding to the next RSID in the source routingsub-header.

MS CID based.

In accordance with the present invention, a number of differentembodiments for implementing decentralized, i.e., distributed, QoScontrol is provided. As a first embodiment, distributed QoS control canbe mobile station 16 CID based. In this case, each relay node 14 storesand maintains a QoS table having CIDs as entries. Each CID is associatedwith a set of QoS parameters. When a relay node 14 receives a MAC PDU,the relay node 14 checks the CID field and schedules furthertransmission based on the QoS parameters corresponding to this CID.

In accordance with a second embodiment, distributed QoS control can beT-CID based in which the T-CID information is transmitted along with aMAC PDU. Each relay node 14 stores and maintains a QoS table havingT-CIDs as entries. Each T-CID is associated with a set of QoSparameters. When a relay node 14 receives a MAC PDU, the relay node 14checks the T-CID field and schedules further transmission based on theQoS parameters corresponding to this T-CID.

In accordance with a fourth arrangement, both centralized/hybrid routeand centralized QoS control are provided. In this case, forwarding relaynodes 14 need not store or maintain any table or may only store ormaintain a route table at the relay node 14 level, i.e., by destinationRS node and not CID. In this case a forwarding QoS and route sub-headeris used. As described above, the forwarding route sub-header can be usedsuch that one sub-header may be used for one group of MAC PDUs to/fromone relay node 14. When more than one group of MAC PDUs is encapsulated,multiple such sub-headers may be used.

An exemplary combined forwarding QoS and route sub-header is describedwith reference to FIG. 11. Combined sub-header 164 includes a 1 bitcontrol field 166. A “1” in control field 166 indicates that thesub-header includes a quantity of MAC PDUs and corresponding QoS fields.A “0” in control field 166 indicates that combined sub-header 164includes a length field and one QoS field.

If control field 166 is “1”, information field 168 includes an 8 bitfield indicating the number of MAC PDUs included as well as one QoS foreach corresponding MAC PDU. If control field 166 is “0”, informationfield 168 includes a 16 bit field indicating the length of the payloadpart of the of PDU to/from the destination relay node 14 as well as an 8bit QoS field, such as the transmission deadline, corresponding to thepayload to/from the destination mobile station 16 or base station 12.

RSID quantity field 170 indicates the quantity of RSIDs in theforwarding path included in the sub-header ordered from next hop RSID todestination RSID. If the quantity is 1, the next hop is the destinationRSID. The sub-header also includes a quantity of RSID fields 172 equalto the value in the quantity of sub-headers field. By way of example,each RSID field can be an 8 bit field containing the subordinate RSID.

An exemplary implementation for this fourth arrangement is described.Initially it is noted that each access relay node 14 can operate bybeing assigned only three connections, namely, basic connection andprimary connections carrying the MAC management messages and aforwarding transport connection for relaying mobile station 16 relatedtraffic and messages of mobile stations 16 attached to the correspondingrelay node 14 (the “access relay node”).

It is contemplated that relay node 14 serves as a forwarding transportconnection which is used for carrying mobile station 16 MAC PDUs thatare to be relayed in the DL and UL directions. The correspondingconnection CID can be expressed as “F-CID”. One F-CID for a relay node14 can be used for both the DL and UL. For the DL case, base station 12maps all mobile station 16 MAC PDUs for mobile stations 16 attached to arelay node 14 to the forwarding transport connection of this relay node14. For the UL case, an access relay node 14 maps all MAC PDUs of themobile stations 16 attached to it to forwarding transport connection ofthis relay node 14. The F-CID is assigned by a base station 12 throughvia a message such as a “DSA-REQ/RSP” message exchange during therouting path setup phase during the initial network entry or networkre-entry of relay node 14.

MAC PDUs of mobile stations 16 associated with an access relay node 14are relayed on the forwarding transport connection between base station12 and this access relay node 14. The mobile station 16 MAC PDUs havingthe same QoS class can be encapsulated into an R-MAC PDU and the QoSinformation field is included in the R-MAC header. One example of QoSinformation is the QoS class ID (3 bits)+deadline (5 bits)=total 8 bits.QoS information includes the QoS class of a carried R-MAC PDU and thetransmission deadline (frame number). For downlink data forwarding, basestation 12 can include the destination relay node 14 F-CID and QoSinformation in the R-MAC header. For the uplink, the access relay node14 includes its F-CID and QoS information in the R-MAC header. Anintermediate relay node 14 can schedule the transmission of the mobilestation 16 MAC PDUs carried in an R-MAC PDU based on QoS informationalong with the received R-MAC PDU, and identify the next hop relay node14 based on F-CID using its routing table. In this case, intermediaterelay nodes 14 do not need to know any QoS profiles and routinginformation for mobile stations 16 that are not directly attached to itand only relay traffic based on QoS class and deadline informationprovided by the sender.

The transmission arrangement of the present invention supports QoS usingthe destination/source relay node 14 F-CID and source QoS control. Whena transmission arrangement uses an access relay node 14 forwardingtransport connection CID and source QoS control information isimplemented, mobile station 16 service flows can be classified into anumber of QoS classes. Mobile station 16 MAC management messages aretransmitted on the basic connections and the primary connections ofmobile stations 16 and can be viewed as two types of services which canbe classified, for example, as QoS 1 and QoS 2, respectively. For sourceQoS control purposes, when new uplink service for a mobile station 16 isestablished, the QoS class of this service can be determined bycorresponding base station 12 and be provided the access relay node 14of this mobile station 16 through a message exchange, i.e., a DSX-Xmessage exchange.

For scheduling purposes, in the downlink case, base station 12 canencapsulate mobile station 16 MAC PDUs having the same QoS class into anR-MAC PDU and calculate the transmission deadline based on QoS profilefor this QoS class. The deadline is expressed as the 5 least significantbits (“LSB”) of the frame number where these mobile station 16 MAC PDUsare transmitted by the access relay node 14. In the uplink case, accessrelay node 14 can encapsulate mobile station 16 MAC PDUs having the sameQoS class into an R-MAC PDU and calculate the transmission deadlinebased on QoS profile for this QoS class. The deadline is the 5 LSB ofthe frame number in which these mobile station 16 MAC PDUs aretransmitted to base station 12. It is noted that the QoS class identityand transmission deadline can be included in the R-MAC header as a QoSinformation field.

An exemplary data packing arrangement constructed in accordance with theprinciples of the present invention is described with reference to theblock diagram of FIG. 12. As shown therein, a routing header 142 may beassociated with a sub-group of MAC PDUs to identify a routing path. Forexample, for a communication from base station 12 to relay node 14 a formobile stations 16 a, 16 b, 16 c and 16 d, a forwarding controlsub-header 174 identifying PDUs destined for relay node 14 b and aforwarding control sub-header 176 and PDUs destined for relay node 14 care included. Sub-headers 174 and 176 can be arranged as described abovebased on whether centralized or decentralized QoS and/or route controlare being used. Relay node 14 a can then generate forwarding controlsub-header 178 identifying PDUs destined for relay node 14 b, i.e., PDUsfor mobile stations 16 a and 16 b. It is contemplated that sub-headers174 and 178 can be the same. It is also noted that sub-headers 174, 176and 178 are used when the corresponding sender controls the QoS and/orthe route.

While FIG. 12 illustrates that a routing header may identify the entireroute (i.e. to the destination relay), the broader inventions are notlimited in this regard. That is to say, a forwarding control sub-headermay only identify part of a route such that a combination of centralizedand decentralized route control may be used. Similar concepts areapplicable to QoS control as well.

As another embodiment, to avoid the potential re-fragmentation in thelast hop in the downlink (“DL”) forwarding path (from relay node 14 tomobile station 16), a upper bound on the size of MAC PDU, e.g., the IEEE802.16e MAC PDU may be set. This upper bound may be exceeded forexample, when multiple MAC PDUs from one connection are encapsulatedinto an R-MAC PDU. To avoid exceeding the upper bound, efficiency may beimproved by reducing some redundancy in the communication. A suppressionsub-header may be used for this purpose.

A suppression sub-header transmission arrangement may be provided asfollows. MAC header suppression can be used when an R-MAC packet is usedto encapsulate multiple MAC PDUs from the same connection to beforwarded by a relay node 14 and there is no centralized QoS/routecontrol. To indicate this, a suppression sub-header that immediatelyfollows an R-MAC header may be used.

According to embodiments, such as those described above wherecentralized QoS/route control is implemented and multiple MAC PDUs fromthe same connection are encapsulated, MAC header suppression ispossible. To indicate such suppression, a suppression sub-header followsthe forwarding control sub-header. If multiple sub-groups areencapsulated in an R-MAC PDU, and MAC PDUs in one of the sub-groups arefrom the same connection, the suppression sub-header can be used and canfollow the forwarding control sub-header for this sub-group.

An exemplary suppression sub-header can include a field indicating thenumber of CIDs among the MAC PDUs from or destined to a relay node 14.This sub-header can also include, for each CID, (1) the CID, (2) thenumber of MAC PDUs having the same CIDs as indicated in the CID field,and (3), the pseudo-noise (“PN”) field in the first MAC PDU having thesame CID.

The present invention also provides an arrangement for enhancingsecurity within systems 10 having relay nodes 14. Such securityenhancement can be provided through the use of a security “tail” in theR-MAC PDU transmitted at the tail end of the R-MAC payload. In such acase, the R-MAC header includes a security tail inclusion indicator bit.This bit, when set, indicates the presence of the security tail. Thesecurity tail can include information used to authenticate the sender,facilitate detection of a modified PDU or detect the retransmission of aPDU. For example, security tail can include a keyed-hash messageauthentication code (“HMAC”) or other message authentication code as maybe known, a packet number, etc.

The above describes arrangements in which a new header and sub-header tosupport the R-MAC layer is provided. It is also contemplated that thepresent invention can be implemented using a protocol stack for anembodiment of the invention where the IEEE 802.16e DL MAC is modified,hereinafter referred to as an Enhanced-MAC (“E-MAC”), to facilitatebackward compatibility with the IEEE 802.16e standard. According to thisembodiment of the invention one MAC PDU encapsulates service data units(“SDU”) from one CID.

While the embodiments described above illustrate formats used to deliverPDUs between a base station 12 and a mobile station 16, additionalextensions to the header fields may be used to permit the packing andtransport of other PDUs destined for or received from other types ofdevices. Some of these PDUs, for example, may be destined for the relaynode itself as part of its control, signaling and maintenance. OtherPDUs may be destined for devices that are attached to the relay node 14through other wired or wireless connections. The relay node 14 may thusbe used to receive and forward PDU traffic from fixed devices such asvideo cameras or from mobile stations 14 that are formatted according toanother radio interface standard but which are arranged for carriage viathe relay node 14/base station 12 network, i.e., system 10.

An exemplary protocol stack for implementing the E-MAC arrangementdescribed above is the same as that shown in FIG. 7 with the exceptionthat the E-MAC PDUs are substituted for R-MAC PDUs. It is also notedthat the four arrangements for implementing traffic control describedabove with respect to R-MAC implements is generally the same for E-MACimplementations, with the exception that multiple MAC PDUs are notsupported in the E-MAC sub-headers.

For example, with respect to the first traffic control arrangementdescribed above, as with the R-MAC embodiment, no control field orsub-header field is needed. With respect to the second traffic controlarrangement described above (centralized QoS control and decentralizedroute control), a QoS control extended sub-header is defined whichincludes a QoS field defining the deadline for the transmission to basestation 12 or mobile station 16, as the case may be.

With respect to the third traffic control arrangement described above(centralized route control and decentralized QoS or hybrid route controland a route table at relay node 14 level), a route extended controlsub-header is defined. As an example, the route extended traffic controlsub-header includes a field for the quantity of RSIDs in the forwardingpath and fields having the list of RSIDs in the forwarding path.

With respect to the fourth traffic control arrangement described above(centralized/hybrid route and centralized QoS control) a QoS routeextended traffic control sub-header is defined. This control sub-headeris the union of the extended control sub-headers described above withrespect to the second and third E-MAC arrangements, i.e., a QoS field aswell as the RSID forwarding path information.

To support traffic forwarding control, it is contemplated that existingdownlink and uplink extended sub-headers can be modified to include theextended sub-headers described above. In the downlink, ES type 6 canhave an 8 bit body size for the QoS sub-header, ES type 7 can have avariable bit body size to support the route sub-header and ES type 8 canhave a variable bit body size to support the combined QoS/routesub-header. In the uplink, ES type 5 can have an 8 bit body size for theQoS sub-header, ES type 6 can have a variable bit body size to supportthe route sub-header and ES type 7 can have a variable bit body size tosupport the combined QoS/route sub-header.

The present invention can be realized in hardware, software, or acombination of hardware and software. Any kind of computing system, orother apparatus adapted for carrying out the methods described herein,is suited to perform the functions described herein.

A typical combination of hardware and software could be a specialized orgeneral purpose computer system having one or more processing elementsand a computer program stored on a storage medium that, when loaded andexecuted, controls the computer system such that it carries out themethods described herein. The present invention can also be embedded ina computer program product, which comprises all the features enablingthe implementation of the methods described herein, and which, whenloaded in a computing system is able to carry out these methods. Storagemedium refers to any volatile or non-volatile storage device.

Computer program or application in the present context means anyexpression, in any language, code or notation, of a set of instructionsintended to cause a system having an information processing capabilityto perform a particular function either directly or after either or bothof the following a) conversion to another language, code or notation; b)reproduction in a different material form. In addition, unless mentionwas made above to the contrary, it should be noted that all of theaccompanying drawings are not to scale. Significantly, this inventioncan be embodied in other specific forms without departing from thespirit or essential attributes thereof, and accordingly, referenceshould be had to the following claims, rather than to the foregoingspecification, as indicating the scope of the invention.

1. A wireless communication method, the method including: receiving aplurality of media access control (“MAC”) packet data units (“PDUs”)corresponding to a plurality of wireless communication connections;grouping the plurality of MAC PDUs into a relay packet; and transmittingthe relay packet.
 2. The method according to claim 1, wherein the relaypacket includes a MAC PDU header, the MAC PDU header includinginformation for identifying each of the plurality of connections.
 3. Themethod according to claim 2, wherein the relay packet includes securityinformation, the presence of security information being indicated by ansecurity inclusion bit in the MAC PDU header.
 4. The method according toclaim 1, wherein grouping includes establishing a plurality ofsub-groups, wherein the relay packet includes a routing header for atleast one sub-group.
 5. The method according to claim 4, wherein therelay packet includes a first routing header for a first sub-group and asecond routing header for a second sub-group.
 6. The method according toclaim 1, wherein transmitting the relay packet includes routing thepacket to a next hop, wherein routing control for the routing iscentralized.
 7. The method according to claim 6, wherein routing isbased on source routing information, the source routing informationincluding at least one relay node ID (“RSID”) in a correspondingforwarding path.
 8. The method according to claim 1, whereintransmitting the relay packet includes routing the packet to a next hop,wherein routing control for the routing is decentralized among at leastone or more relay nodes.
 9. The method according to claim 8, whereinrouting is based on at least one of a connection ID (“CID”), relay nodeID (“RSID”) and T-CID.
 10. The method according to claim 1, whereintransmitting the relay packet includes controlling the packet based on aquality of service (“QoS”), wherein QoS control is decentralized amongat least one or more relay nodes.
 11. The method according to claim 10,wherein QoS control is based on at least one of a connection ID (“CID”),relay node ID (“RSID”) and T-CID.
 12. The method according to Claim I,wherein transmitting the relay packet includes controlling the packetbased on a quality of service (“QoS”), wherein QoS control iscentralized.
 13. The method according to claim 12, wherein controllingthe packet based on a quality D of service (“QoS”) includes evaluatingQoS information in at least one of the received MAC PDUs and schedulingtransmission of the relay packet based on the evaluated QoS information.14. The method according to claim 1, wherein PDUs in the downlinkdirection are backward compatible with the IEEE 802.16e standard, thebackward compatibility being obtained by encapsulating service dataunits in MAC PDUs.
 15. A system for wireless communication, the systemincluding at least one relay node, the relay node being arranged to:receive a plurality of media access control (“MAC”) packet data units(“PDUs”) corresponding to a plurality of wireless communicationconnections; group the plurality of MAC PDUs into a relay packet; andtransmit the relay packet.
 16. The system according to claim 15, whereinthe relay packet includes a MAC PDU header, the MAC PDU header includinginformation for identifying each of the plurality of connections. 17.The system according to claim 16, wherein the relay packet includessecurity information, the presence of security information beingindicated by an security inclusion bit in the MAC PDU header.
 18. Thesystem according to claim 15, wherein grouping includes establishing aplurality of sub-groups, wherein the relay packet includes a routingheader for at least one sub-group.
 19. The system according to claim 18,wherein the relay packet includes a first routing header for a firstsub-group and a second routing header for a second sub-group.
 20. Thesystem according to claim 15, further including a base station in datacommunication with the at least one relay node, wherein transmitting therelay packet includes routing the packet to a next hop, wherein routingcontrol for the routing is centralized and provided by the base station.21. The system according to claim 15, wherein transmitting the relaypacket includes routing the packet to a next hop, wherein routingcontrol for the routing is decentralized among at least one or morerelay nodes.
 22. The system according to claim 15, wherein transmittingthe relay packet includes controlling the packet based on a quality ofservice (“QoS”), wherein QoS control is decentralized among the at leastone or more relay nodes.
 23. The system according to claim 15, furtherincluding a base station in data communication with the at least onerelay node, wherein transmitting the relay packet by the at least onerelay node includes controlling the packet based on a quality of service(“QoS”), wherein QoS control is centralized and provided by the basestation.
 24. The system according to claim 23, wherein controlling thepacket based on a quality of service (“QoS”) includes evaluating QoSinformation in at least one of the received MAC PDUs and schedulingtransmission of the relay packet by the at least one relay node based onthe evaluated QoS information.